Since a polyimide resin has characteristics such as superior heat resistance, mechanical strength and insulation property or low dielectric constant, a polyimide resin is used widely as an insulating material or protective material in electric or electronic parts including various elements or electronic substrates such as multilayered wiring board. Also, in order to insulate or protect a minute point selectively in precision electric or electronic parts, polyimide resin which has been provided with patterning to a desired shape is used.
Generally, a polyimide resin is formed by subjecting polyamic acid obtained by polymerizing a tetracarboxylic dianhydride component and a diamine component in a polar organic solvent to heat treatment at a temperature of approximately 300° C. Therefore, polyimide products for an electronic material are often supplied as a solution of a polyimide precursor, such as polyamic acid. In producing electric or electronic parts, a solution of a polyimide precursor is supplied to a site where an insulating material or protective material is to be formed by a method such as coating or injection, etc. and thereafter the solution of the polyimide precursor is subjected to heat treatment at a high temperature of approximately 300° C. to form the insulating material or protective material.
Conventional methods for forming an insulating material or protective material made of a polyimide resin from a polyimide precursor have problems in which such conventional methods are not applicable to material which is weak to heat, because the conventional methods require heat treatment at a high temperature. Accordingly, a polyimide precursor composition which is capable of forming a polyimide resin by the treatment at a low temperature, i.e., approximately 200° C., has been developed (for example, Patent Document 1).
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2009-19113